Photographic emulsions containing mercury salts



peratures above normal.

United States Paten O PHOTOGRAPHIC EMULSIONS CONTAINING MERCURY SALTS Burt H. Carroll and Thomas F. Murray, Rochester, N. Y., assignors to Eastman Kodak Company, Rochester, N. Y., a corporation of New Jersey Application November 8, 1952, SerialNo. 319,612

6 Claims. c1. 95-4 This invention relates to fog-inhibiting agents and stabilizers for photographic emulsions and to photographic emulsions containing them.

It is known that photographic emulsions, particularly ultra-sensitive emulsions or those containing optical sensitizers exhibit a tendency to form a deposit of silver in the emulsion upon development. This deposit extends more or less uniformly over the entire emulsion and is known as fog. Photographic fog is of two types: local and general. Local fog is formed by exposure of the film or plate at undesired points as by a light leak in the camera. General fog is formed in a number of ways. It may be caused by the conditions of high temperature or humidity or unusually long time of storage. The nature of the emulsion may also produce chemical fog as well as the conditions of development of the emulsion as by development for protracted periods of time or at tem- We are primarily concerned with fog and sensitivity changes in photographic films produced by storage under adverse conditions of temperature and humidity or for prolonged periods of time before exposure and development.

General fog and loss of sensitivity of the emulsion are especially likely to occur when the sensitive material is stored under conditions other than ideal, that is, under conditions of high temperature and humidity, as in tropical regions.

It is an object of the invention to provide novel antifogging or fog-inhibiting compounds for emulsions. A further object is to provide anti-fogging agents which stabilize the initial sensitivity of the emulsion. A still further object is to provide anti-fogging agents which improve the keeping of the emulsion in tropical regions. Other objects will appear from the following description of our invention.

No Drawing.

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are made soon after coating. However, when sensitometric measurements are made after appreciable intervals of time under tropical or dry conditions of storage at elevated temperatures, these compounds do stabilize photographic speed and maintain fog at a low level. The mercury salt may be added to the emulsion in solution in any convenient solvent, such as water or alcohol.

The preparation of silver halide emulsions involves three separate operations: (1) the emulsification and digestion or ripening of the silver halide, (2) the freeing of the emulsion from excess soluble salts, usually by washing, (3) the second digestion or after-ripening to' obtain increased sensitivity. (Mees, The Theory of the Photographic Process, 1942.) The fog-inhibiting agents may be added at any stage, e. g., after the final digestion. The most useful concentration range of fog inhibitor is from about 0.05 to 0.25 mg. of fog inhibitor per gram mole of silver halide in the emulsion. This amount will vary, e. g., depending on the silver halide used.

The emulsions may be chemically sensitized by any of the accepted procedures; for example, they may be digested with naturally active gelatin, or sulfur compounds may be added such as those described in Sheppard U. S. Patents 1,574,944 and 1,623,499, and Sheppard and Brigham U. '8. Patent 2,410,689.

The emulsions may also be treated with salts of the noble metals such as ruthenium, rhodium, palladium, iridium and platinum, all of which belong to Group VIII of the periodic table of elements and have an atomic weight greater than 100. Representative compounds are ammonium chloropalladate, potassium chloroplatinate and sodium chloropalladite, which are used for sensitizing in amounts below that which produces any substantial fog These objects are accomplished by incorporating in a silver halide emulsion a simple mercuric or mercurous salt of an inorganic or organic acid.

The principal purpose of our invention is to provide a means for maintaining the sensitivity and fog of silver halide emulsions at or close to initial optimum values under keeping conditions of high temperature and humidity. The fog inhibitors which we propose to use are added to the emulsion at any'stage during the process of manufacture prior to coating the emulsion, to avoid loss of sensitivity and to inhibit the growth of incubation or keeping fog with passage of time under nonideal conditions of storage.

The mercury salts which may be used for the purpose of our invention include mercury halides, e. g., mercuric chloride, mercurous chloride, mercuric bromide, mercurous bromide, mercuric iodide and mercurous iodide, mercuric nitrate, mercurous nitrate, mercurous sulfate, and mercuric acetate, and the corresponding complexes formed with an excess of acid anion, e. g., K2Hg(CN)4 and K2HgBr4.

A solution of the mercury salt which we employ, when added in suitable concentration before coating to unsensitized or optically sensitized silver halide emulsions, does inhibition, as described in Smith and Trivelli U. S. Patent 2,448,060, and as antifoggants in higher amounts, as described in Trivelli and Smith U. S. Patents 2,566,245

1 and 2,566,263.

The emulsions may also be chemically sensitized with gold salts as described in Waller and Dodd U. S. Patent 2,399,083, Damschroder U. S. Patent 2,597,856, and Yutzyand Leermakers U. S. Patent 2,597,915. Suitable compounds are potassium chloroaurite, potassium aurithiocyanate, potassium chloroaurate, auric trichloride and 2-aurosulfobenzothiazole methochloride.

The emulsions may also be chemically sensitized with reducing agents such as stannous salts (Carroll U. S.

Patent 2,487,850), polyamines such as diethylene triamine (Lowe and Jones U. S. Patent 2,518,698), polyamines such as spermine (Lowe and Allen U. S. Patent 2,521,925), or bis-(B-aminoethyl) sulfide and its watersoluble salts (Lowe and Jones U. S. Patent 2,521,926).

The antifoggant and stabilizing action was determined by incubation of the emulsions for one week. The results of aging tests are tabulated below and compare speed, gamma and fog of the emulsions with and without the stabilizing compound. A high speed orthochromatic bromoiodide emulsion was used and it was treated as described in the following examples.

Example 1 To 1 liter of a gelatino-silver bromoiodide emulsion containing 0.24 mole of silver halide per liter, optically sensitized with 20 mg. of 3,3'-diethyl-9-methylthiacarbocyanine bromide per liter, containing 10 cc. of 8% saponin solution, there were added the amounts of mercuric salts in alcohol solution, shown in the following table. The emulsion was coated on glass plates and the coated plates together with other plates coated at the same time and with the same emulsion to which no mercuric salt had been added were exposed on an Eastman type IIb Sensitometer and developed for five minutes at 68 F.

in a developer of the following formula:

Patented Dec. 27, 1955 3 Grams Upon testing the fresh and incubated samples for N-methyl-p-am-inophenolsulfate; 2.5 speed; gamma-- and fog, the following results were ob- Sodium sulfite (desiccated) 30 tained:

Fresh Test After Incubation Compound mg./mole 7 Speed Galmna, Fog.v Speed Gamma Fog Control 250 1.40.- .09 205 1.46 .12 (RTriethylene tetramine 36 295: 1463 .11 315 1.48 .20 I mercuric chloride 12 295 1'. 54 .09 400 1. 36 .14

Hydroquinone 2.5 Examplet4 f A medium speed gel'atino-silver bromoiodide emulsion Potassiumbromide 0.5

Water to 1 liter.

was digested with 20 mg. per mole of silver halide of allylthiourea and divided. into portions to which were added the mercury compounds shown in the following table; These portions were coated on cellulose acetate film support, exposed on aIb Sensitometer, and developed for4 minutes in a developer having the same composition as' that used in Example 3. Upon testingfor speed, gamma and fog before and after incubation for 4 weeks Fresh Coating After Incubation mg. Compound mole;

Speed Gamma Fog Speed Gamma Fog Control 540 1.62 .08 500 1.55 .13 Coating containing mercuric chloride 0.21 450 1.82 .08 460 1.51 .04v Coating containing mercuric to i e 0.08 500 1.73 .08 560 1.55 .08-

at 120 F., the following results were obtained:

Example 2 I Fresh Test After Incubation mg. To portions of a gelatmo-silver bromoiodide emulsion mole V containing 0.24 mole of silver halide per liter, digested Speed Gamma Speed Gamma Fog with a sulfur sensitizer such as disclosed in Sheppard U. S. Patent 1,574,944,, and potassium chloroaurate,. and gfggf 255 1124 I 210 109 optically sensitized with a mixture of cyanine and mero- 35 1 .072 220 1.20 .07- 225 1.15 .26

ercunc rocyanine dyes, there were addedvarying amounts. of mer mide n 235 L24 )9, 195 L09 I 40 curous sulfate, and the emulsionswere coated and. treated Mercuric iov as described in Example 1. Upon testing for speed, gggifi'iii: 245 L08 gamma and: fog, the following results were obtained: trate .0195 255-- 1.25 .08 215 1.12 .34 Do .039 265 1.23 .09" 225 1.10 .36 40 Fresh. Coating After Incubation Compound g Speed Gamma Fog Speed Gamma Fog It can be seen that when. larger amounts, say 4 mg. per mole, are used, the speed is considerably reduced.

Example 3 Grams N-methyl-p-aminophenol sulfate 2.2 Hydroquinone 8.8 Sodium sulfite (desiccated) 96 Sodium carbonate, monohydrate 56 Potassium bromide 5 Water to 1 liter.

Instead of incorporation in. the silver halide emulsion the: fog-inhibitors of. our invention may be incorporated in a colloid layer suchas a gelatin layer on one or both sides of the filmor they may be incorporated in a processing bath such as adeveloper or pro-bath.

The fog-inhibitingagents which We have described'may be used:in various kinds of photographic emulsions. In addition to being useful in ordinary non-sensitized emulsions they may also be used inorthochromatic, panchromatic and X-ray emulsions. If used with sensitizing dyes, they may be added to the emulsion before or after the dyes are added. Various: silver salts may be used as the sensitive salt, such as silver bromide, silver iodide, silver chloride. or mixed silver halides. The mercury. compounds may-be usedin emulsions; intended for color photography, for example, emulsions containing color-forming couplers, or emulsions to be developed by solutions containing couplers.

Thev dispersing agents. may be. gelatin-or other colloid such as. collodion, albumen, cellulose derivatives or synthetic resins.

It will be understood that We contemplate as included within our invention all modifications and equivalents falling within the scope of the appended claims.

What we claim is:

1. A silver halide emulsion substantially free from increase in fog and loss of speed upon storage, containing as the only heavy metal salt other than silver halide, an appreciable and fog-inhibiting amount, but not more than about 0.25 mg. per mole of silver halide in the emulsion, of a mercury salt selected from the class consisting of mercuric chloride, mercurous chloride, mercuric bromide, mercurous bromide, mercuric iodide, mercurous iodide, mercuric nitrate, mercurous nitrate, mercurous sulfate, mercuric acetate, K2Hg(CN)i and KzHgBm.

2. A silver halide emulsion substantially free from increase in fog and loss of speed upon storage, containing as the only heavy metal salt other than silver halide, an appreciable and fog-inhibiting amount, but not more than about 0.25 mg. per mole of silver halide in the emulsion, of mercuric chloride.

3. A silver halide emulsion substantially free from increase in fog and loss of speed upon storage, containing as the only heavy metal salt other than silver halide, an appreciable and fog-inhibiting amount, but not more than about 0.25 mg. per mole of silver halide in the emulslon, of mercuric iodide.

4. The method of reducing fog and loss of speed upon storage of a silver halide emulsion, which comprises incorporating in said emulsion at any stage prior to coating, as the only heavy metal salt other than silver halide, an appreciable and fog-inhibiting amount, but not more than about 0.25 mg. per mole of silver halide in said emulsion, of a mercury salt selected from the class consisting of mercuric chloride, mercurous chloride, mercuric bromide, mercurous bromide, mercuric iodide, mercurous iodide, mercuric nitrate, mercurous nitrate, mercurous sulfate, mercuric acetate, KzHg(CN)4 and KaHgBra.

5. The method of reducing fog and loss of speed upon storage of a silver halide emulsion, which comprises incorporating in said emulsion at any stage prior to coating, as the only heavy metal salt other than silver halide, an appreciable and fog-inhibiting amount, but not more than about 0.25 mg. per mole of silver halide in said emulsion, of mercuric chloride.

6. The method of reducing fog and loss of speed upon storage of a silver halide emulsion, which comprises incorporating in said emulsion at any stage prior to coating, as the only heavy metal salt other than silver halide, an appreciable and fog-inhibiting amount, but not more than about 0.25 mg. per mole of silver halide in said emulsion, of mercuric iodide.

References Cited in the file of this patent UNITED STATES PATENTS 2,540,086 Baldsiefen et al Feb. 6, 1951 

1. A SILVER HALIDE EMULSION SUBSTANTIALLY FREE FROM INCREASE IN FOG AND LOSS OF SPEED UPON STORAGE, CONTAINING AS THE ONLY HEAVY METAL SALT OTHER THAN SILVER HALIDE, AN APPRECIABLE AND FOG-INHIBITING AMOUNT, BUT NOT MORE THAN ABOUT 0.25 MG. PER MOLE OF SILVER HALIDE IN THE EMULSION, OF A MERCURY SALT SELECTED FROM THE CLASS CONSISTING OF MERCURIC CHLORIDE, MERCUROUS CHLORIDE, MERCURIC BROMIDE, MERCUROUS BROMIDE, MERCUROUS IODIDE, MERCUROUS IODIDE, MERCURIC NITRATE, MERCUROUS NITRATE, MERCUROUS SULFATE, MERCURIC ACETATE, K3HG(CN)4 AND K2HGBR4. 